Hey all I ve been working on relocating the underhood fuse box harness to an under the dash tuck. I don't plan on running AC again.

So lets talk OEM rad fans. I want to keep my OEM rad fan wired to the ECU, I figure it knows better than any toggle switch I can rig up.

So that has been extended and rerouted, along with a whole pile of other accessories on that harness. Hell the end is in sight!

But im slightly stumped on my AC fan. I ve been extending everything else with matching wire from another harness. I don't have enough OEM wire at the moment to make this thing long enough.

What would you all do with the second fan? Delete for wieght reduction? Wire into the Rad fan?

If I extend it in its OEM configuration, with all else AC related gone, it would still come on with the AC button if I want it to right? Hit the snowflake for extra engine cooling

Just trying to decide what to do with this thing. Not sure if its just unnecessary weight that gets in the way of a future recirculated wastegate setup.

I'm running my two Mishimoto fans in series.

And mounted them to the front of the rad after changing their polarity to push air through the rad.

I believe it wont come on with just the button.. It needs high pressure from the AC coolant. Which is no longer there.

Now I have never ran bothfans, never bothered. Been happy with the plastic oem fan. What ever model that comes on. But I do have my single fan controlled by the EGR solinoid out put. It turns the fan on, above 190° and dose not shut off unless Im at full throttle. That might be an easy short wire job for you.

The button can be used as a switch.

It just requires you to wire it in that way. The temp sensor tells the ecu to turn on the relay which would all be bypassed if you decide to wire in the AC button as a switch.

The easiest method I found was to use a jumper cable bypassing the AC relay at the fuse box, meaning both fans would come on by the control of the ecu. But I decided to scrap that mod and just run both fans in series. And I've pretty much got them on full time with link.

If the hvac cabin fan is on and you hit the a/c button the a/c fan comes on, or if you have it in the defrost position, no need to re-wire anything as long as you're using the same wiring from the fans/relays.



Fan works regardless, it's the compressor clutch that won't kick in without the switch.

I deleted my AC lines, compressor and condensor. With the switch on, it didn't turn on the oem fan.. And if I understand what you're saying, it's that it will?

We are talking about deleting the AC right?

If Jason has it right Im going to hold off deleting the wiring to the AC fan a little longer. Its hard to build a car ground up hypothetically without the money to incorporate planned upgrades just yet. There is still time though

I m also pondering if I can fit one or both fans on the otherside of the rad to push air instead of pull. Or run one slim fan there in series with the stock rad fan.

Although im sure there are recirculated external waste gates out there that could fit in there on stock fans depending on the turbo and its plumbing.

Everything in mine is deleted AC wise except for the fan and stock wiring, it works exactly as I said, as long as the the hvac is on, push the ac button and the ac fan comes on.

I went ahead and deleted the AC compressor and condensor plugs too. Extended the fan plug for the time being. Hope the theoretic harness mods didnt cause me too many issues lol! Got the crazy thing almost how I want it, lots more soldering to do.

I removed alot of extra wiring between rear defrost/wiper/antenna and cruise control. have to verify what still works before I go any further, but I past the point of no return a long time ago

Come to think of it, I don't recall checking to see if the fan would turn on with the HVAC on... Hmm

Actually, Nevermind.. The light doesn't come on with the HVAC on. So I would have tested it.

I can confirm what Jason is saying. I too have my AC components removed, and as long as the HVAC fan is turn on, pressing the AC button activates the AC radiator fan.

Wicked! Thanks Scott. I should be ready to test the interior and accessory harnessess soon, not supposing I need the engine harness plugged in yet to do that

Seems that it doesnt work so flawlessly just yet. I dont think the alarm is causing me issues. Its kind of hard to tell without doors , an ecu, stereo or engine plugged in.

Headlights, tailLights, and foglights dont all work properly, and horn stays on. on the positive half the lights work properly and the HVAC blower, chimes and wipers work lmao.

Couldnt get the AC fan to switch on but thats currently the least of my issues. Yikes.

So I am trying to diagnose a wierd short here. Is there a problem with moving a ground wire to a different ground location? I thought the purpose was to just get the current back to the battery through the chassis. I figured everything should work as long as it is grounded. and even if it all has its own individual ground point vs a junction of a bunch of grounds together at the same point?

I am now referring to the whole cars wiring harness and components. not just fans

Horn is switch ground I believe. Common on a 1g but not sure on a 2g. This means when you push the horn you are completing ground circuit. If you connected ground then that is the reason the horn is always on.

doesnt appear that way to me :



I have had my head in so many diagrams now lol.

Headlights just for fun to see if anyone can spark some thoughts.

No 2g isn't that way, I know that cause Terry and I got the same horns but had to connect them differently.

Sorry read that wrong. So I would double check your horn switches. My first guess is that they are making contact still.

Or the relay is toast.

With my 2010 MDX horns, unless they're grounded on the body, they'll never make a sound.

in the fuse panel, locate both the cooling fan relay and the a/c fan relay.

locate both signal pins (ecu triggered for cooling and push button for a/c)

now that you have located both signal pins open up the fuse panel, disconnect the a/c switch signal and split the ecu signal to both relays.

both fans will come on under their own circuit